Process of dyeing wool-polyacrylo-



United States Patent PROCESS OF DYEING WOOL-POLYACRYLO- NITRILE BLEND Lejaren Arthur Hiller, Jr., Waynesboro, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August 28, 1952,

Serial No. 306,936

1 Claim. (Cl. s-21 This invention relates to unionor cross-dyeing of textiles comprised of mixed fibers, one of which is derived from a polyacrylonitrile fiber or a fiber of a copolymer of at least 40% acrylonitrile and one or more copolymerizable ethylenically unsaturated compounds.

Acrylonitrile polymer fibers have been found to possess 2,772,943 Patented Dec. 4, 1956 the dye intended for them with the attainment of full bright colors unclouded by partial masking by the basic color used on the polyacrylonitrile fibers.

Certain basic dyes are preferred in this invention, for

5 some basic dyes have affinities for W001, even under the a yellow basic dye of C. I. 841, yellow basic dye of C. I.

excellent properties when prepared in theform of spun yarns. Staples and continuous filament yarns of acrylonitrile polymer and copolymer blend well with wool, cotton, or staples of rayon, cellulose derivatives, nylon, polyesters and other synthetics to produce very desirable fabrics. uniform or control coloration is acute and must be solved if such mixed fabrics are to attain commercial status. Up to the present time no method for satisfactorily dyeing acrylonitrile polymer fiber blends, such as wool/ acrylonitrile polymer fiber blends, has been developed and the only procedure for obtaining a dyed product of this type involves separate dyeings of the fibers before blending. Such a procedure is costly.

Unionor cross-dyeing of mixed fibers is an old story and has been practiced many years with wool and cotton, wool and rayon, rayon and cellulose acetate, etc. Notwithstanding all the knowledge and tricks and quirks that have been developed inthe art over the many years, dyeing of acrylonitrile fibers alone has been a major problem and to couple the insecure dyeing techniques with the necessity for uniform dyeing of blends rapidly pyramids the difficulties.

Accordingly, an object of this invention is to provide an improved dyeing procedure for uniformly or crossdyeing textiles comprised of acrylonitrile polymer fibers in combination with other textile fibers. Other objects will be apparent from the description that follows.

It has been found that certain dyes when applied to fiber blends using appropriate conditions are capable of dyeing the polyacrylonitrile fibers selectively without appreciably coloring the wool, cotton, rayon, nylon, polyester, cellulose acetate or other fibers blended therewith. Thus, it is possible to dye uniformly fiber blends containing polyacrylon'itrile fibers through the use of these selected dyes and conditions in combination with suitable dyes for the other fiber or fibers of the blend. Similarly, cross-dyeing of textiles composedtin part of acrylonitrile polymer fibers may be secured by omitting the dye for the other fiber or by using a contrasting color or any desired combination of colors. The objects of this invention are accomplished by dyeing the fibers derived from polyacrylonitrile, with certain basic dyes in dye baths the acidities of which are in a pH range of from about 3.0 to about 5.0. Preferably, the dyeings are carried out at or near the boil of the aqueous dye bath and preferably, when. two or more dyeing steps are used, the textile, following the dyeing with the selected basic dye, is subjected to scouring with soap or .some other detergent solution. This scouring step re- .moves from the non-polyacrylonitrile fibers loosely .held

color and permits these fibers to receive subsequently In such mixtures, however, the problem of q 655, brown basic dyes of C. I. 331 and 332. The cyanine dyes which are condensation products of trimethylindolenine chloride with various other organic groups are very satisfactory. For example, a specific orange cyanine dye and a useful red cyanine dye have the following structures:

Other basic dyes useful in the practice of this invention are those corresponding to Colour Index numbers 658, 659, 661, 663, 788, 793, 876 and 924.

Some basic dyes that have undesirable afilnity for wool are violet basic dye of C. I. 681, blues of C. I. 728 and 729, violet of C. I. 680, violet of C. I. 682,

red of C. I. 749, red of C. I. 752. The first five of' these are characterized as strongly basic triphenylmethane dyes containing three alkyl or aryl substituted nitrogen atoms. The red dyes have a carboxyl group or a substituted carboxyl group. The distribution of these various groups in the dyestuff molecules leads to wool affinity, and steps must be taken to avoid or to decrease the affinity as, for example, by placing certain surfactants in the dye bath as disclosed and claimed in the copending application of Bidgood, Serial No. 306,935. For the purposes of this invention it is, therefore, preferred to use basic dyes free of strongly basic triphenylmethane structures and free of acidic groups, although these dyes can be used under certain conditions.

Wool is commonly dyed with basic dyes at neutral or very slightly acid conditions. Under these dyeing conditions, normal for W001, poly-acrylonitrile and wool take up about equal amounts of the basic dyestufi such as green basic dye of C. I. 662. However, it is indeed surprising that wool will not permanently accept the dye at all at the lower pH of this invention and that the dyeing of acrylonitrile polymer is enhanced by increasing the acidity into the range of 3 to 5 pH.

It is generally undesirable to have wool dyed with basic dyes, because basic dyes even now available usually show poor fastness on wool. Therefore, in dyeing mixtures of wool and acrylonitrile polymer, the wool is dyed either simultaneously or separately using an acid dye.

Ina preferred embodiment of this invention a good de- 3 tergent scouring following the application of the basic dye is very effective to the securing of fast bright coloration on the textile of blended fibers. The selection of the detergent will depend upon its effectiveness in removing the basic dye from the particular fiber blended with the polyacrylonitrile fiber. Among the most effective detergents are non-basic soaps, the fatty alcohol sulfates, dodecyl trimethyl ammonium chloride and other similar acid or neutral quaternary ammonium salts. In the scouring of wool, alkaline soaps, and alkaline detergents are generally not used or are carefully or sparingly used inasmuch as they may damage the wool, especially since the scouring treatments are usually conducted at temperatures near the boil. On the other hand, with cotton or viscose rayon as the other fiber blended with the polyacrylonitrile fiber the alkaline detergents may even be selected in preference to the acid detergents. Thus, the selection of the detergent will be governed somewhat by the nature of the fiber blended with the polyacrylonitrile fiber.

To illustrate and explain this invention further, the following examples are given.

EXAMPLE I To illustrate the relative afiinity for a basic dye for several types of fibers, samples of the several types of fibers listed in Table I below were dyed together in a dye bath containing 2% green basic dye of C. I. 662 based on the total weight of fiber present. This dyeing was carried out at the boil (98 C.) for one hour at a pH of 3.5, the pH being adjusted with acetic acid. Suflicient dyestuff was present in the bath to dye tofull shade all the fiber present. At the end of the hour the samples were rinsed thoroughly to remove dye bath liquor and were then scoured for minutes at the boil in 0.5% Palmolive soap solution in order to remove loosely held dye. The fiber samples were analyzed for dye uptake by measuring the reflected color in a differential color reflectance meter. These readings were related to dye concentration in the fiber. Relative dyeabilities were calculated from these results on a scale where acrylonitrile homopolymer fiber was assigned the value of 100. The relative affinities of the different fibers for this representative basic dye are given in Table I.

These data show that acrylonitrile polymer fibers may be dyed selectively with this basic dycstuff in the presence of any of the other fibers listed.

EXAMPLE II A number of samples of polyacrylonitrile fiber, drawn 4X, were prepared with an equal weight of wool and each mixture was subjected to the dyeing procedure outlined in Example I, using the following basic dyes:

1. Green basic dye of C. I. 662,

. Green basic dye of C. I. 657,

. Blue basic dye of C. I. 922,

. Yellow basic dye of C. I. 815,

. The orange cyanine dye shown above and The red cyanine dye shown structurally above.

(DUI-bulb.)

All of these dyes colored the polyacrylonitrile fibers to full shade dyeing while leaving the wool untouched or only very slightly stained after the boil-off scouring treatment described under Example I. v

To complete the experiments, the above'numbered samples, the polyacrylontrile fibers of which were dyed.

with the various basic dyes mentioned, were next dyed in the usual manner with the acid dyestuffs listed in the same order below:

. Violet of C. I. 1080,

. Green of C. I. 666,

. Red of C. I. 176,

. Yellow of C. I. 639,

Green of C. I. 735 and 10 Violet of C. I. 1080.

Most of these dyes were chosen to give contrasting colors and it was noted that full dye shades were developed on the wool with the several acid dyes without in any way changing the shade or brightness of color on the acrylonitrile polymer fibers. Thus, it is demonstrated that each fiber of the mixed fiber samples could be dyed selectively.

EXAMPLE III Table II Basic Dyes Acid Dyes 1. Green of O. I. 662. 1. Green of C. I. 666. 2. Blue of C. I. 922. 2. Blue of Pr. 12. 3. Yellow of O. I. 815. I 3. Yellow of C. I. 639. 4. The red cyanine dye depleted 4. Violet of G. I. 1080. I above.

*AAITC foreign prototype number.

Speckled fabrics were obtained from the first dyeing of each sample showing the acrylonitrile polymer selectively colored, while the wool remained substantially uncolored, thereby causing the speckled effect. Following the second dyeing with the acid dyestuffs the wool portion is.also shown to be selectively dyed without in any way altering the color previously taken up by the polyacrylonitrile fibers.

EXAMPLE IV In a similar test the fabric of Example III was first dyed with green basic dye of C. I. 662 and after rinsing and scouring, the sample was next dyed with green acid dye of C. I. 666 to produce closely matched greens and a fabric uniform in shade.

EXAMPLE V EXAMPLE VI Dyeing blends of polyacrylonitrile fibers and fibers of regenerated cellulose from viscose can be accomplished as follows:

a. Staple prepared from polyacrylonitrile filaments, drawn 4X, was blended with staples of regenerated celluplaced in a dye bath containing green basic dye of C. I.

' 662. The general procedure outlined in Example I was followed. Only the polyacrylonitrile fibers were dyed.

After scouring and rinsing, as previously described, the (5 fiber blend was entered into a dye bath containing blue lose produced by theviscose process and the blend was' airrama direct dye of C. I. 518-. In this bath theregenerated cellulose filaments were readily dyed without in any way affecting the colored polyacrylonitrile fibers.

b. The same general procedure was employed to dye a fabric prepared from spun yarn made up as a 50/50 blend of 4X drawn polyacrylonitrile fiber and regenerated cellulose fiber, the spun ;yarn being used in both the warp and filling. The dyeing with "basic dyeswas car- 'ried out firstto dye the polyacrylonitrile fibers and, after rinsing and scouring, the regenerated cellulose fibers were dyed with direct dyestuffs. The basic .dye was applied as described under Example I. The direct dye was applied as follows: Sufiicient direct dyestufi was present in the dye bath to dye to a full shade all the regenerated cellulose fiberpresent. The samples were placed in the dye bath at the boil (98 C.) and kept there 1 hour. At the end of 45 minutes sodium sulfate was added "in amount equal in weight to the direct dyestuff originally in the bath to aid in exhausting the dye. The following dye combinations set forth in Table III below were used:

Basic Color Direct Color Green of C. I. 594. Blue of C. I. 518. Yellow of O. I. 365. Violet of C. I. 394.

1. Green of C. I. 662. 2. Blue of G. I. 922. 3. Green of O. I. 662. 4. Blue of C. I. 922.

With all these combinations very satisfactory dyeing was obtained.

0. The procedure just described under b was reversed and the direct dye applied to the regenerated cellulose part of the fabric first followed by the application of the basic dye to the polyacrylonitrile fiber part of the fabric. The following dye combination was used in this example: direct violet dye of C. I. 394 and basic red dye of C. I. 677. The blend was dyed to different shades of violet.

d. A basic dye, green of C. I. 662, and a direct dye, yellow of C. I. 365, were placed in the same dye bath and a piece of the fabric described under paragraph b above was dyed for one hour at the boil at a pH of 3.5 in the presence of a small amount of sodium sulfate (equal to weight of direct dyestuff). The polyacrylonitrile fibers were dyed a deep green and the regenerated cellulose fibers a bright yellow.

The above procedures obviously may be applied to other cellulosic fiber blends with polyacrylonitrile fibers as for example, cotton, linen, etc. which exhibit similar dyeing properties to regenerated cellulose. Any of the dyes mentioned above as requiring preventatives for the dyeing of wool in blends by certain basic dyes, for example, the blues of C. I. 728 and 729, also must be kept from dyeing cellulose, since these dyes tend to stain the cellulose, and it is preferred to dye the cellulose with direct dyes.

EXAMPLE VII Dyeings of polyacrylonitrile fiber of the type above described and nylon staple were carried out in an identical manner to the foregoing examples of polyacrylonitrilewool dyeings. The polyacrylonitrile fibers were selectively dyed with basic dyes and the nylon fibers with acid dyes. For instance, green basic dye of C. I. 662, and violet acid dye of C. i. 1080 gave excellent dyeings. The same precautions taken with certain basic dyes with the wool blends aud the cellulose blends are taken with the nylon blends.

EXAMPLE VIII A sample comprised of polyacrylonitrile continuous filament yarn drawn 8X and nylon continuous filament yarn was dyed first in a dye bath containing a basic dye- ;stuif, green of C. I. 6 62, under pressure at 225 F. for 30 minutes. After rinsing and scouring as earlier described, ,the sample was subjected to dyeing with an acid dye,

yellow of (3.1.63.9, also under pressure at 225 F. for 30 minutes. Bot-h typesof filaments were dyed to a full shade, the polyacrylonitrilefilaments being green and the nylon filaments being yellow. i i

EXAMPLE 1x ozncsm nincsmmcznfi canton The combination dyed with the blue dye was subjected to dyeing with a typical sulfonated solubilized acetate dye defined as 2,4-dinitroaniline ethyl hydroxy ethyl aniline sulfuric ester. Full depth of color was secured on both types of fibers by this procedure. However, since the dispersed'acetate dyes also dye polyacrylonitrile fiber, it is preferred, in this case, to dye the polyacrylonitrile first, otherwise a small amount of staining of the polyacrylonitrile fiber will occur through the action of the dispersed acetate dye. In the case of the solubilized colors no such staining will occur and such colors may be applied first, if desired. Therefore, the use of these dyestuffs is a preferred procedure.

EXAMPLE X Two samples of blended fibers of polyacrylonitrile staple and staple of a polycondensate of terephthalic acid and ethylene glycol were subjected in two experiments to dyeing first with the basic dyestuifs blue of C. I. 922. and green of C. I. 662. After rinsing and scouring, the first sampleblend was subjected to dyeing with the dispersed acetate dye of Example IX and the second blend with the water soluble acetate dye used in Example IX. A small amount of paraphenyl phenol was added to these dye baths to aid the dyeing of the polyester. In this case the polyacrylonitrile fibers were dyed a bright blue and green while the polyester fibers were colored scarlet and violet. As in Example IX, some staining of the polyacrylonitrile fiber was noted when the dispersed acetate dye was used first, but not when the solubilized acetate dye was used first.

In adjusting the pH of the dye baths of this invention a large number of acids may be used. For example, acetic acid, hydroxyacetic acid, propionic acid, hydrochloric acid, sulfuric acid, phosphoric acid and formic acid are usable. For most purposes, acetic acid is satisfactory and is generally used.

As is evident in the foregoing description this invention enables polyacrylonitrile fibers to be blended with other textile fibers and uniform coloration applied to the fiber blend and to textiles made therefrom. Uniform dyeings or cross-dyeing may be prepared as desired. The blends may be made up of two or more different materials. Under the conditions of dyeing the polyacrylonitrile fibers dyed with the selective basic dyestufi possess good fastness properties toward washing and in many cases good fastness toward sunlight. The process may be carried out in the usual dye house equipment without the need of any special equipment and without going through a costly and complicated procedure.

While the invention has been primarily described in terms of dyeing polyacrylonitrile fiber or staple blends, it is also applicable to combinations of continuous filament yarns of polyacrylonitrile combined in any way with other types of filament or spun yarns. Dyeings at elevated temperatures in pressure dyeing equipment to give deep shades of basic dyes on highly drawn polyacrylonitrile fibers also give very satisfactory results. Also numerous copolymers wherein the acrylonitrile content is 40% or more, such as mentioned in U. S. Patent 7 2,436,926 to Jacobson are dyeable with the basic dyes of this invention and may be used in blends with any of the other non-acrylonitrile polymer fibers and dyed in the manner previously described with excellent results. Also, the basic modified polyacrylonitrile polymers described in U. S. Patent 2,491,471, e. g. acrylonitrile, 2 vinyl pyridene 94/6, may be used to good advantage. The polyacrylonitrile homopolymer fibers or copolymer fibers may be drawn in the range from 2X to 10X or more or less. Similarly, the fibers blended with the acrylonitrile polymer fibers may be prepared or modified in various ways and may be oriented or undrawn. While filamentary material has been used in the description of this invention, blends in other forms may also be dyed by the processes of this invention. The conditions of time, temperature, concentration, pressure and equipment may be varied appreciably. With the maintenance of the critical pHof 3.0 to 5.0, the basic dyes can be made to dye the acrylonitrile polymer fibers selectively in the presence or absence of other dyes, such as acid or direct dyes, used for dyeing the non-acrylonitrile polymer component of the blend.

By this invention a great variety of dyed blends is made available for use in the production of useful articles, such as flat fabrics, suiting material, auto tops, blankets, tablecloths and the like.

I claim:

A process for selectively dyeing a fibrous acrylonitrile polymer, containing at least 40% acrylonitrile by weight, in a blend with wool which comprises subjecting the blend to the action of an aqueous dye bath containing a basic cyanine dye and having a pH between about 3.0 and about 5.0, removing any dye from the wool and then subjecting the resultant blend to the action of an aqueous dye bath containing an acid dye.

References Cited in the file of this patent Dyeing with Coal Tar Dyestufls by Whittaker and Wilcock, fifth ed., 1949, London; Balliere, Tindall and Cos. Publisher, page 165.

Amer. Dyes. Reporter for Dec. 12, 1949, pages P925- P928 incl. 

